Most conventional pharmaceuticals currently in use for the treatment of serious disorders such as cancer and inflammatory diseases do not selectively accumulate at the site of disease [Bosslet et al., 58, 1195-1201 Cancer Res. (1998)]. For example, intravenously administered drugs distribute evenly within the different organs and tissues of the body, rather than selectively accumulating at the site of disease.
One approach to circumvent the disadvantages of conventional pharmacological therapies involves the preferential delivery of a bioactive agent to the site of disease by means of a binding molecule specific for a pathology-associated marker [Neri & Bicknell (2005), 5, 436-446 Nature Rev. Cancer]. The selective targeting of the drug to the diseased tissue will ultimately result in an increased local concentration at its site of action, sparing normal organs from the unwanted effects of the bioactive agent used to confer a pharmacological benefit (e.g., a growth factor, an enzyme, a hormone, an anti-inflammatory drug, a cytotoxic drug, a cytokine, a radionuclide, a photosensitizer). In most cases, this will lead to an improved therapeutic index of the delivered pharmaceutical, i.e. a higher efficacy with minimized side effects. Indeed, the favourable toxicity profile of site-specific therapeutics may open new avenues in the therapy of angiogenesis-related diseases, allowing the systemic administration of highly potent and promising agents, which are currently either given at suboptimal doses or whose clinical application has to date been impeded by unacceptable side-effects when applied in an unmodified form.
Ligand-based pharmacodelivery strategies fundamentally rely on the identification of good-quality markers of pathology, allowing a clear-cut discrimination between diseased tissues and healthy organs. Monoclonal antibodies and their fragments represent the preferred agents for pharmacodelivery applications [Rybak et al. 2, 22-40 Chem. Med. Chem (2007); Shrama et al., 5, 147-159 Nat. Rev. Drug Discovery (2006)], but globular protein mutants [Binz and Plückthun, 23, 1257-1268 Nature Biotechnology (2005)], peptides [Sergeeva et al., 58, 1622-1654, Adv. Drug. Deliv. Rev. (2006)] and even small organic ligands [Low et al., 41, 120-129, Acc. Chem. Res. (2008)] are also increasingly being used.
Antibody-based targeted delivery of bioactive agents to sites of angiogenesis as a therapeutic strategy for cancer treatment has been described. In the case of inflammatory disorders, antibody-based targeted delivery is much less well studied. The applicant has previously demonstrated that the ED-A domain of fibronectin, and the ED-B domain of fibronectin, two marker of angiogenesis, are expressed in the arthritic paws in the collagen-induced mouse model of rheumatoid arthritis. Using both radioactive and fluorescent techniques, the human monoclonal antibody F8, specific to ED-A, and the human monoclonal antibody L19, specific to ED-B, were found to selectively localize at sites of inflammation in vivo, following intravenous administration. When such antibodies were fused to the anti-inflammatory cytokine interleukin-10 the conjugate strong therapeutic activity was also shown (PCT/EP2007/004044, PCT/EP2008/009070). Nevertheless there remains a need in the art for further antibodies which can be employed in ligand-based pharmacodelivery applications for the treatment and diagnosis of diseases, such as cancer and inflammatory disorders.
Collagen
Collagens are the major structural components of the extracellular matrix. A coordinated and regulated expression of the different collagens is important for correct development in vertebrates and collagen mutations are involved in several inherited connective tissue disorders. Among them, Collagen type II (COL2A1) is the most abundant in cartilage [Strom C. M and Upholt W. B., Nuc Acid Res (1984), 12, 1025-1038 and Cheah K. S. et al., (1985) Biochem J, 229, 287-303]. COL2A1 is synthetized by chondrocytes during embryogenesis and de novo in pathological conditions in the adult. COL2A1 is a homotrimer composed of three α1(II) chains. These are secreted as long immature procollagen molecules that undergo proteolytic cleavage by collagenases in the extracellular environment, thereby forming the mature type II Collagen. COL2A1 forms heteropolymers with Collagen IX and Collagen XI, creating the fibrillar network typical of cartilage [Eyre D., (2002) Arthritis Res, 4, 30-35]. It has been known since the late 1980s that mutations in the COL2A1 gene are the cause of several hereditary disorders related to the abnormal development of bones and cartilage, including spondyloepiphyseal dysplasia congenital type [Lee B. et al., Science (1989), 244, 978-980], spondyloepimetaphyseal dysplasia strudwick type and many others.
Moreover different techniques have been used to investigate the expression of COL2A1 in normal and rheumatoid human articular cartilage. Normal COL2A1 is expressed evenly in healthy tissue, while diseased joints show strong enhancement of type II collagen [Aigner T. et al., (1992) Virchows Archives B Cell Pathol Incl Mol Pathol, 62, 337-345]. This evident change in the extracellular matrix composition is due to a failure of maintaining the homeostasis of the cartilage fibrillar network [Gouttenoire J. et al., (2004) Biorheology, 41, 535-542]. COL2A1 is reasonably well conserved between mouse, rat and man.